Adaptation of the 3H-Leucine Incorporation Technique to Measure Heterotrophic Activity Associated with Biofilm on the Blades of the Seaweed Sargassum spp

• Published in: Microbial ecology Vol. 65; no. 2; pp. 424 - 436
• Main Authors: Coelho-Souza, Sergio A., Miranda, Marcio R., Salgado, Leonardo T., Coutinho, Ricardo, Guimaraes, Jean R. D.
• Format: Journal Article
• Language: English
• Published: New York Springer-Verlag 01.02.2013; Springer
• Subjects: Animal, plant and microbial ecology; Bacteria - metabolism; Bacteria - radiation effects; Bacteriology; Biofilms; Biological and medical sciences; Biomedical and Life Sciences; Ecology; Fundamental and applied biological sciences. Psychology; Geoecology/Natural Processes; Heterotrophic Processes; Leucine - metabolism; Life Sciences; Light; Methods; Microbial Ecology; Microbiology; Microscopy, Electron, Scanning; Miscellaneous; Nature Conservation; Sargassum - microbiology; Seaweed - microbiology; Various environments (extraatmospheric space, air, water); Water Microbiology; Water Quality/Water Pollution; Diuron; Extracellular Polymeric Substance; Leucine Incorporation; Incorporation Rate; Detritus; Incorporation; Radiolabelling; Algae; Ecology; Leucine; Sargassum; Marine environment; Heterokontophyta; Marine algae; Biofilm; Bacteria; Phaeophyceae; Plant microorganism relation
• ISSN: 0095-3628; 1432-184X
• DOI: 10.1007/s00248-012-0116-9

The ecological interaction between microorganisms and seaweeds depends on the production of secondary compounds that can influence microbial diversity in the water column and the composition of reef environments. We adapted the 3 H-leucine incorporation technique to measure bacterial activity in biofilms associated with the blades of the macroalgae Sargassum spp. We evaluated (1) if the epiphytic bacteria on the blades were more active in detritus or in the biofilm, (2) substrate saturation and linearity of 3 H-leucine incorporation, (3) the influence of specific metabolic inhibitors during 3 H-leucine incorporation under the presence or absence of natural and artificial light, and (4) the efficiency of radiolabeled protein extraction. Scanning electron microscopy showed heterogeneous distribution of bacteria, diatoms, and polymeric extracellular secretions. Active bacteria were present in both biofilm and detritus on the blades. The highest 3 H-leucine incorporation was obtained when incubating blades not colonized by macroepibionts. Incubations done under field conditions reported higher 3 H-leucine incorporation than in the laboratory. Light quality and sampling manipulation seemed to be the main factors behind this difference. The use of specific metabolic inhibitors confirmed that bacteria are the main group incorporating 3 H-leucine but their association with primary production suggested a symbiotic relationship between bacteria, diatoms, and the seaweed.